1. [Field of the Invention]
The present invention relates to a motor having a drive control circuit, and particularly, to a technique effectively applied to a brushless motor for use in an electric power steering apparatus.
2. [Related Art Statement]
In recent years, many proposals have been made for motors in which a drive control circuit for selecting an exciting coil or for controlling the amount of supplied power is integrated with a motor body, to respond to demands for downsizing and modularizing of devices. For example, Japanese Patent Application Laid-Open Publication No. 2001-213336 discloses an electric hydraulic power steering apparatus in which a DC brushless motor and a drive control circuit of the motor are incorporated together. Further, Japanese Patent Application Laid-Open Publications No. 2000-177612, No. 10-86831 and No. 8-150945 each disclose a structure in which a motor having a brush is integrated with a drive control circuit.
However, in this kind of motor integrated with a circuit, a board mounting electric components is contained in a housing. In this structure, a unit containing a circuit is merely integrated with a motor body. A problem hence arises in that the size of the apparatus is enlarged by dimensions equivalent to the unit. The electric components mounted on the board have various shapes and sizes. If those components are mounted on a flat board, the housing must be shaped to fit the tallest component. A useless space then appears over shorter components. Although the above publications provide some countermeasures by bending the board into an L-shape to extend along the outer surface of a gearbox, for example, a useless space still remains over smaller components. The space efficiency therefore deteriorates in the area of the unit and hinders downsizing of the motor.